The present invention relates to a power generation system.
For a better understanding of the invention, an explanation is first made for a typical coal gasification composite power generation system of the prior art with reference to FIG. 7.
The gasifier unit is composed essentially of a primary combustor 01 and a succeedingly disposed reductor 07. The primary combustor 01 is supplied with coal and char as the fuel. The term "char" is intended to mean a pulverous carbon deposited in the gasifier unit without being availed for the gasification. The primary combustor 01 is operated under a high temperature combustion of such supplied fuel under a reducing condition (an air ratio of less than 1) with compressed air. Coal is supplied to the primary combustor 01 from a coal supply duct 02. Char is recovered after the gasifier unit by a char collector 03 and returned to the primary combustor 01 via a char supply duct 04 as fuel supplement. A turbo compressor 05 is employed for supplying the compressed air to the combustor via an air duct 06. The combustion gas enters the reductor 07, where the intrinsic gasification of the coal fuel additionally supplied thereto from the supply duct 02 is realized according to the following reaction scheme: EQU C+H.sub.2 O.fwdarw.CO+H.sub.2
The resulting product gas is cooled through a heat economizer 08 and is then passed to the char collector 03 via a gas duct 09 to recover the deposited char. The collected char is returned to the primary combustor 01 via the char supply duct 04 as explained previously.
The product gas leaving the char collector 03 enters then a dry desulfurizer 011 via a gas duct 010, where it is desulfurized. The desulfurized gas passes then through a dust remover 013 via a gas duct 012 to remove the entrained dust particles, before it is fed to a secondary combustor 015 constituting the burner for a gas turbine 016 via a gas duct 014, where it is burned completely by compressed air supplied from the turbo compressor 05. The resulting combustion gas drives the gas turbine 016 for generating electric power by a generator 029 driven by the gas turbine. The gas turbine inlet temperature is controlled by adjusting the feed rate of the combustion air or, if the air feed rate is set at a constant value, by adjusting the feed rate of coal to the gasifier unit.
The turbine exhaust gas is sent to a waste heat steam generator 018, where the sensible heat of the turbine exhaust gas is recovered by utilizing it for steam generation before it is discharged out to the atmosphere via a chimney 019.
The steam produced in the steam generator 018 is supplied via a steam main 020 to a steam turbine 021 for an additional power generation. The spent steam is condensed in a condenser 022 and the condensate is returned to the steam generator 018 and to the heat economizer 08 via each water feed line 024, 025 by a feed pump 023 under pressure elevation. The steam generated in the heat economizer 08 is also supplied to the steam main 020 via a steam line 026 and is used for the power generation in the steam turbine 021. On combustion of the coal fuel in the gasification unit, molten slag or ash in a form of particles is formed, which fall down into a slag tank 026 and are discharged to the outside of the system through a discharge duct 027. The dust collected in the dust remover 013 is taken out of the system via a discharge duct 028.
By the gas turbine 016, the generator 029 is driven to generate electric power.
Coal gasification composite power generation systems of the prior art as explained above have exhibited many problems left unsolved, such as the following: